If you have Calibre set up for your ereader, all you have to do is highlight the txt file you want to convert and click the 'convert file' icon in calibre. It will bring up a screen for conversion. Just make sure that the output file in the upper right hand corner is epub (change it if it's not) and it should convert the file.

Suggestion: in the "Convert" dialogue window, click on the "TXT Input" Icon and then check the "Treat each line as a paragraph" box. Otherwise, your .txt file might convert to .epub as a single paragraph..... not good.

Suggestion: in the "Convert" dialogue window, click on the "TXT Input" Icon and then check the "Treat each line as a paragraph" box. Otherwise, your .txt file might convert to .epub as a single paragraph..... not good.

There are many options and many forms of text, that's why Treat each line as a paragraph isn't the default option.

Suggestion: in the "Convert" dialogue window, click on the "TXT Input" Icon and then check the "Treat each line as a paragraph" box. Otherwise, your .txt file might convert to .epub as a single paragraph..... not good.

This works well if your text document is formatted well for your ereader. By "formatted well" I mean that the only CR/LFs are between paragraphs. This lets you change font sizes or rotate the book 90 degrees and your ereader will be able to break lines where needed for best display.

However, there are lots of text format books that are not formatted well. These usually have a CR/LF break at the end of each 80 character line, i.e., not at the end of sentences or paragraphs. To get these to convert well, you should check "Assume print formatting", not "Treat each line as a paragraph."